his section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Field of the Invention
The present invention relates to the field of data transmission along a tubular body. More specifically, the invention relates to the acoustic transmission of data along pipes within a wellbore. The present invention further relates to a hybrid wired-and-wireless transmission system for transmitting data along a downhole tubular string and to an in-wellbore tool incident to completion operations.
General Discussion of Technology
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling to a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thus formed between the string of casing and the surrounding formations.
A cementing operation is typically conducted in order to fill or “squeeze” the annular area with cement. The combination of cement and casing strengthens the wellbore and facilitates the isolation of formations behind the casing.
It is common to place several strings of casing having progressively smaller outer diameters into the wellbore. A first string may be referred to as surface casing. The surface casing serves to isolate and protect the shallower, fresh water-bearing aquifers from contamination by drilling fluids. Accordingly, this casing string is almost always cemented entirely back to the surface. A next smaller string of casing is then run into the wellbore.
A process of drilling and then cementing progressively smaller strings of casing is repeated several times below the surface casing until the well has reached total depth. In some instances, the final string of casing is a liner, that is, a string of casing that is not tied back to the surface. The final string of casing, referred to as a production casing, is also typically cemented into place.
In some completions, the production casing (or liner) has swell packers spaced across production intervals. This creates annular compartments for isolation of the zones during stimulation treatments and production. In this instance, the annulus may simply be packed with sand.
As part of the completion process, the production casing is perforated at a desired level. This means that lateral holes are shot through the casing and the cement column surrounding the casing. The perforations allow reservoir fluids to flow into the wellbore. In the case of swell packers or individual compartments, the perforating gun penetrates the casing, allowing reservoir fluids to flow from the rock formation into the wellbore along a corresponding zone.
After perforating, the formation is typically fractured in the various zones. Fracturing consists of injecting an aqueous fluid into a formation at such high pressures and rates that the reservoir rock parts and forms a network of fractures. The fracturing fluid is typically mixed with a proppant material such as sand, crushed granite, ceramic beads or other granular materials. The proppant serves to hold the fracture(s) open after the hydraulic pressures are released.
In order to further stimulate the formation and to clean the near-wellbore regions downhole, an operator may choose to “acidize” the formations. This is done by injecting an acid solution down the wellbore and through the perforations. The use of an acidizing solution is particularly beneficial when the formation comprises carbonate rock. In operation, the completion company injects a concentrated formic acid or other acidic composition into the wellbore, and directs the fluid into selected zones of interest. The acid helps to dissolve carbonate material, thereby opening up porous channels through which hydrocarbon fluids may flow into the wellbore. In addition, the acid helps to dissolve drilling mud that may have invaded the formation and that remains along the wellbore.
In some instances, the wellbore is left uneased along the pay zones. This means that no liner string is used. This is known as an open hole completion. To support the open wellbore and to prevent the migration of sand and fines into the wellbore, a filtering screen is typically placed along the subsurface reservoirs. A column of sand may also be installed around the filtering screen, thereby forming a gravel pack. In this instance, the wellbore is not perforated and fractured, although it may still be acid-treated.
The application of hydraulic fracturing and/or acid stimulation as described above is a routine part of petroleum industry operations as applied to individual hydrocarbon-producing formations (or “pay zones”). Such pay zones may represent up to about 60 meters (100 feet) of gross, vertical thickness of subterranean formation. More recently, wells are being completed through a producing formation horizontally, with the horizontal portion extending possibly 5,000, 10,000 or even 15,000 feet.
When there are multiple or layered formations to be hydraulically fractured, or a very thick hydrocarbon-bearing formation (over about 40 meters, or 131 feet), or where an extended-reach horizontal well is being completed, then more complex treatment techniques are required to obtain treatment of the entire target formation. In this respect, the operating company must isolate various zones or sections to ensure that each separate zone is not only perforated, but adequately fractured and treated. In this way the operator is sure that fracturing fluid and proppant are being injected through each set of perforations and into each zone of interest to effectively increase the flow capacity at each desired depth.
The isolation of various zones for pre-production treatment requires that the intervals be treated in stages. It is desirable to obtain data from the wellbore during the completion operation. In the oil and gas industry, communication systems have been introduced for monitoring downhole conditions and wellbore orientation during drilling. Such systems include mud pressure pulse transmission, or so-called mud pulse telemetry, which uses the drilling and wellbore fluids as a data transmission medium. Such also includes acoustic telemetry which uses the drill pipe as a transmission medium. Such also includes radiofrequency signals wherein electrodes placed in the pin and box ends of pipe joints are tuned to receive RF signals, which are transmitted along the pipe joints.
It is also known to use fiber optic cables and electrical wires in a wellbore for communicating data. Cables and wires transmit data front a downhole sensor or measurement device during production. However, cables and wires generally are not used in connection with perforating, fracturing and acid-treating operations.
Still further, it is known to run logging tools and downhole sensors into a wellbore at the end of a wireline during production or remediation operations. Such operations are generally referred to as well logging. However, logging operations cannot be conducted during perforating, fracturing and acid-treating operations.
Therefore, a need exists for a downhole telemetry network that enables sensors to wirelessly transmit data from various zones along a wellbore in real time, and then transmit that data wirelessly to a tool in the wellbore during completion operations. Further, a need exists for a method of receiving data during a wellbore completion operation from a telemetry network that combines wireless and wired data transmission in real time.